Exogenous ketones are synthetic ketones consumed in supplement form that mimic the state of ketosis — i.e., they cause a temporary increase in the concentration of beta-hydroxybutyrate (a ketone body) in the blood.[1][2][3][4] Such supplements are called “exogenous” because they come from an external source (e.g., a supplement) rather than being produced naturally by the body.
The active ingredient in exogenous ketone supplements is typically beta-hydroxybutyrate (a.k.a. 3-hydroxybutyrate), which is often attached to an ester — a ketone ester — or a sodium/potassium/magnesium salt — a ketone salt.[5][6][7] However, some exogenous ketone supplements contain a ketone precursor (e.g., 1,3-butanediol) that is metabolized by the liver after ingestion to produce beta-hydroxybutyrate.[5][6][7]